When carrying out work underwater, in particular when inserting an object into the underwater floor, the resultant sound is radiated from the object into the water surrounding it. Underwater sound dampers are known for reducing underwater sound, also referred to as waterborne sound, i.e. the sound in the water.
Underwater floors are understood to mean the fixed floor body below a water column. An underwater floor in the context of the present invention is a seafloor or the bed of a dock or inland water such as a lake or river. The objects that are usually inserted into the underwater floor when carrying out work underwater are foundation bodies such as piles or construction parts such as wall elements, which are inserted by means of drilling or driving into the underwater floor. Within the context of the invention, other sound-emitting devices such as a drilling pipe can also be understood as objects to be inserted into the underwater floor.
When drilling, vibrational driving or pulsed driving, considerable sound emissions are emitted from the object inserted into the underwater floor, but also from the underwater floor, into the surrounding water. The sound is produced at the friction surface between the object and the underwater floor and is transmitted therefrom into the surrounding water.
Underwater sound, as is produced when working underwater as described above, can be perceived by marine mammals, such as porpoises and seals, over large distances. Any animal that uses its hearing for communication, orientation and for foraging is in particular adversely affected by underwater sound. Permanent hearing damage can thus result in death in these animals.
Various techniques are known for reducing the sound. In a bubble curtain, compressed air tubes are laid around the edge of the underwater construction site. These are connected to compressors and pump compressed air into the tubes on the underwater floor. This compressed air rises in the form of a curtain of air bubbles and thus forms a physical-acoustic, sound-absorbing barrier.
Instead of the volatile air bubbles that are difficult to control, enveloping bodies made of resilient material can also be used as sound-reducing elements. In this case, a multiplicity of sound-reducing elements are arranged on a support structure. This is a net, for example, which can be flexibly stretched around the sound source in the water. The nets are held in place on the underwater floor by means of weights. The sound-reducing elements and the support structure are referred to as a whole as an underwater sound damper. An underwater sound damper also has a damping effect and can be adapted precisely to the expected sound spectrum. An underwater sound damper is less susceptible to sea currents and is optimally effective over the entire relevant frequency range. Furthermore, in an underwater sound damper, a continuous supply of compressed air like that needed for bubble curtains is not required.
DE 10 2008 017 418 A1 discloses an underwater sound damper for reducing underwater sound. This consists of a multiplicity of damping elements for reducing underwater sound, which are spaced apart from one another and are distributed over a support structure, for example a net. The support structure is arranged around a sound source at the operation site. A sound source is, for example, a pile that is inserted into the underwater floor by means of driving or drilling.
The generic document, DE 10 2004 043 128 A1, relates to a pile guiding apparatus for guiding a pile to be driven into the bed of a body of water, which pile is surrounded by an inner and an outer textile curtain, so that the bubbles leaving a nozzle arrangement rise between the two textile curtains. For this purpose, discharge openings are located in the radial direction between the inner textile curtain and the outer textile curtain. Since the bubbles leaving the exhaust openings and rising cannot pass either of the two textile curtains, they remain concentrated in the tube-shaped space between the two textile curtains until they reach the water surface. The nozzle arrangement consists of two rigid legs, which are connected to two joints, and therefore the nozzle arrangement can be opened in order to introduce the pile laterally into the nozzle arrangement. The movable legs are then closed so that the pile is surrounded and fixed in its correct position.
DE 10 2012 206 907 A1 discloses an apparatus for reducing the propagation of sound, vibrations and pressure surges in a liquid when inserting an object into a substrate having a plurality of damping bodies that can be filled with a gas and a support, on which the damping bodies can be arranged in a suitable position relative to one another. The support comprises a frame having vertical and horizontal pipe elements that are arranged perpendicularly to one another, which frame is movable between a closed position and an open position by means of joints. Alternatively, the frame regions made up of horizontal pipe elements can be coupled to one another by means of cables in order to allow for particularly space-saving storage or space-saving transport of the apparatus when not in use.
WO 2013/102459 A2 describes a method and an apparatus for handling an underwater sound damper in the region of an offshore construction site, in particular for a pile to be inserted into the underwater floor. The apparatus disclosed comprises a retaining device on which a first end of the underwater sound damper is retained, and a second end of the underwater sound damper that is remote from the first end of the underwater sound damper and can be positioned so as to be movable relative to the retaining device, in particular moved away from the retaining device.
Furthermore, DE 10 2006 008 095 A1 relates to shell-shaped segments made of a sound-absorbing material, which are connected by hinges and which together form a rigid sound-insulation sleeve.
GB 2509208 A also relates to a rigid sound-insulation envelope of this type.